The long-term objective of this research project is to identify the neural circuit that is responsible for the generation of an example of muco-ciliary locomotion. The experiments proposed in this grant will provide insights into how a well defined neural circuit can be modified by a Pavlovian conditioning procedure to support the generation of a conditional response. To achieve these goals, a multi-disciplinary approach to the study of the cellular and synaptic basis of motor behavior will be carried out in the marine mollusc Hermissenda; a preparation that has proven useful in biophysical, biochemical, and molecular studies of learning. The research will use a combination of cellular neurophysiological and behavioral techniques to study ciliary locomotor behavior in intact animals and semi-intact preparations. One primary goal of the research is to identify the motor neurons that support the generation of ciliary movement. We will identify the neural elements of the central pattern generating network and determine how the properties of the network contribute to the locomotor program and the generation of ciliary locomotion. A second major goal is to determine how the circuit supporting locomotor behavior can be modulated by illumination and modified by an example of associative learning, Pavlovian conditioning. We will examine site of cellular and synaptic plasticity produced by Pavlovian conditioning in the network that is postsynaptic to the conditioned stimulus pathway. This experimental approach will expand our understanding of conditioning in Hermissenda by identifying other potential loci of plasticity produced by conditioning. These studies will help elucidate general principles underlying the organization of neural systems generating behavior and its modification by experience.